[PATCH][PR64971]Convert function pointer to Pmode when emit call

[Jeff Law]

On 08/04/2016 08:32 AM, Renlin Li wrote:
> Hi all,
>
> In the case of PR64971
> (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64971),
> the compiler ICE when compiling gcc.c-torture/compile/pr37433.c with
> ilp32 abi.
>
> As we know, in aarch64 ilp32, the ptr_mode is SImode while Pmode is
> still DImode. It means all address should be DImode, and the backend
> defines the patterns with this assumption.
>
> The generic part expand_expr_addr_expr () function however generates a
> SYMBOL_REF with SImode, it's later used as the address of a MEM rtx
> pattern in a call expression. There is no matching pattern for this
> SImode address, that's why gcc ICEs.
> (symbol_ref/f:SI ("*.LC0") [flags 0x82] <var_decl 0x3ffb7fa1200 *.LC0>)
>
> But here, I think what expand_expr_addr_expr does is correct. In this
> particular case, expand_expr_addr_expr is not generating an address.
> According to the source code, it's generating a function pointer, and
> later this pointer is used in a call expression. So SImode should be
> right in this case.
>
> The behavior of the test case is, get the address of a piece of memory,
> cast it into a function pointer, and call the function. IIUC, the flow
> is like this:
> CALL_EXPR ( NOP_EXPR (ADDR_EXPR ()))
>
> NOP_EXPR here is to convert the address into a function pointer which
> should be ptr_mode (SImode). So it's the responsibility of call expander
> to convert the pointer into Pmode to create legal call rtx patern.
>
> In the test case, there are two functions. The first function generates
> function calls with a SYMBOL_REF as address, the second one generates a
> REG as address. They are all of ptr_mode.
> However, prepare_call_address () will convert the REG into Pmode to make
> it as a legal address while SYMBOL_REF is missed. That's why I add the
> code there.
>
> And I want to change the PR64971 into a middle-end issue. The ICE
> manifests in aarch64 target, but I believe this should be a generic
> problem for targets which define ptr_mode different from Pmode.
>
> There is a test case already, so I didn't add one.
> aarch64-none-elf regression test Okay, aarch64-linux bootstrap Okay.
> But I believe this may not help as the default abi is LP64.
>
> It will be great if Andrew you can help to do regression test in your
> aarch64 ilp32 environment.
>
> And I double checked that, the backend fix can be removed without any
> problem. It's good to expose middle-end bugs.
>
> Okay for trunk and backport to branch 6?
>
> gcc/ChangeLog:
>
> 2016-08-04  Renlin Li  <renlin.li@arm.com>
>
>         PR middle-end/64971
>     * calls.c (prepare_call_address): Convert funexp to Pmode when
>         necessary.
>     * config/aarch64/aarch64.md (sibcall): Remove fix for PR 64971.
>     (sibcall_value): Likewise.
OK.

jeff